The invention relates to a reinforcement for surfaces of structural elements or buildings. The subject of the invention also includes corresponding structural elements and building components, as well as materials, a special polymer material in particular.
Reinforcements are well known in the art in structural engineering. They are used to coat structural elements and building components, primarily ones of concrete, in particular for strengthening or repair purposes. As is known, use is made for this purpose of reinforcements applied by lamination or adhesion in situ or again of prefabricated and bonded reinforcements of fiber assemblies with bonding agents or adhesives, all of them of high or maximum strength and similarly high or maximum modulus of elasticity. The strengthening or repair requirement can be more or less optimally satisfied with such reinforcements. However, it has been found in practical operation that the moisture almost always present on the surface and in the interior of the base is detrimental to the long-term durability of the connection between reinforcement and base transmitting transverse strains and tensile stresses and even to the long-term durability of the coated concrete itself. No satisfactory solution has been found up to the present for the resulting problems of bond strength and durability.
The object of the invention is accordingly to develop a reinforcement or suitable materials which, while preserving strength and rigidity adequate for broad applications, especially as regards reliable relief of stress on the base by adequate transfer of stress to the reinforcement, permits long-term escape of moisture from the area of the base.
The basic concept of the invention is interactive application for reinforcement of bonding or adhesive layer materials which possess the combined characteristics of high tensile strength and high tensile modulus of elasticity in keeping with the purpose of bonding on the structural element or building component, along with vapor permeability determined by the durability requirement. A structure such as this is considered above all for layered reinforcements in which a fiber assembly is installed by aspiration of binder into the bonding layer applied to the base. The binder remaining on the base then simultaneously represents the adhesive layer. The vapor permeable binder provided as claimed for the invention accordingly allows outward diffusion of the moisture in the base. Then again, there are structures with prefabricated layered material consisting of a fiber assembly and binder which is fastened to the base by means of a vapor-permeable adhesive layer claimed for the invention. For the most part the laminated material binder is in this case also vapor-permeable in accordance with the invention, but in theory an application is also possible which involves a laminated material binder which is not or is very slightly vapor-permeable, an application in which the always essential vapor-permeable adhesive layer leads to admittedly slower long-term removal of moisture from the base, as a result of transverse diffusion in the edge areas of the base. Suitable configuration of the reinforcement can promote such diffusion. On the whole, then, the teaching claimed for the invention represents significant technical progress in structure reinforcement engineering.
In addition to any materials which are possibly already available as such or may be readily produced for a combined application in accordance with the invention, the use of adhesive layer or binder or primer or cover layer material based on polyurethane is another feature of the invention which has proved itself in practical application, especially for laminated fiber reinforcements in which the binder also constitutes the adhesive layer. Special polyurethanes claimed for the invention, which themselves are also new and have proved themselves in practical application are products of reaction of low molecular polyols which possess rigid chains of molecules which are at least partly linear, with aromatic or heterocyclic polyisocyanates. The data relating to values for reinforcement materials permit valid compromise optimization with respect to divergent or contrary tendencies in action of the parameters for vapor permeability, having a water vapor permeation resistance uH2O or a maximum of approximately 350 mxe2x88x921 or within the range of 500 to approximately 3000 mxe2x88x921, and strength or modulus of elasticity of the binder and adhesive layer material for broad application, having a tensile modulus of elasticity of a minimum of approximately 1000 N/nm2 or in the range of approximately 3000 N/nm2 to 6000 N.nm2.
Another embodiment of the invention for extreme areas of requirements set for strength or rigidity of the binder and adhesive layer material, especially in conjunction with the features in the associated claims, opens up ways of optimizing while preserving the vapor permeability required. The underlying concept is achievement of higher strength and rigidity values for the adhesive layer or base layer within a vapor-permeable reinforcement layer in which an especially high tensile stress or shear stress exists between reinforcement and base or even in the reinforcement itself, higher strength and rigidity values for the adhesive layer or base layer at the expense of vapor permeability, the intermediate areas being adequately dimensioned with high vapor permeability for moisture removal. This development greatly increases the area of application of the invention. Extension of reinforcement in the high-load areas over the entire thickness of the reinforcement, that is, not merely to the thickness of the adhesive layer, can be accomplished easily in layering in situ by suitable surface distribution of different binder materials on the base before installation of the fiber assembly. On the other hand, this alternative of the invention may always be applied also to prefabricated laminated materials by installation on the base sections of adhesive layer sections clearly delimited on the basis of difference in composition before the prefabricated laminated materials are installed. This applies in suitable applications even to use of prefabricated laminated materials of low or no vapor permeability, when adequate moisture removal may be achieved through edge and transverse diffusion, or if desired by resorting to suitable layered reinforcement configurations.
It is claimed for the invention that primarily epoxy-based polymer materials curing under damp conditions or on a damp base are to be considered as adhesives and/or binders in the case of the alternatives discussed above and other alternatives. The high moduli of elasticity of the epoxy polymers may be used in this way also in the process of removal of moisture from a structure.